1. Field of the Invention
This invention relates generally to orbital welders, and more particularly to a novel orbital welder facilitating easier tube alignment and capable of forming non-planar welds.
2. Description of the Background Art
Orbital welders are widely used in the construction of fluid handling systems, for example semiconductor processing equipment. Known orbital welders join metal tubes in an end-to-end fashion by forming a flat, circular weld around the circumference of the tube's open end. One problem encountered by conventional orbital welders is that the ends of the tubes which are to be joined must be carefully aligned prior to performing the welding operation. Additionally, because known orbital welders are limited to forming flat, circular welds (i.e., a circular weld lying in a single plane), special tube preparation is required to weld a cross or a tee ("T") joint.
FIG. 1 is a top plan view of a typical orbital welder 100, which includes an insulating housing 102, tube clamps 104 and 106, a rotor 108, a weld tip 110, and a rotation and voltage controller 112. Clamps 104 and 106 hold tubes 114 and 116, respectively, in position for welding, and are maintained at a common voltage (e.g., ground) and in electrical contact with tubes 114 and 116. Rotor 108 is disposed within housing 102 so as to be rotatable about an axis 118 passing through the center of the open ends of tubes 114 and 116. Housing 102 provides electrical insulation between rotor 108 and clamps 104 and 106. Rotation and voltage controller 112 functions to rotate rotor 108 within housing 102, and to apply a voltage, via rotor 108, to attached weld tip 110.
FIG. 2 shows a cross-sectional view of orbital welder 100. As controller 112 rotates rotor 108 about axis 118 and applies a high voltage to weld tip 110, an arc weld 202 is formed between the open ends of tubes 114 and 116. Because clamps 104 and 106 are held at the common voltage, they must be displaced a safe distance from weld tip 110, so as not to generate an arc therebetween. The distance between clamps 104 and 106 and the open ends of tubes 114 and 116 makes alignment of the open ends of tubes 114 and 116 more difficult. Moreover, the interior chambers of known orbital welders are dark, and, therefore, visual confirmation of proper alignment is difficult.
FIG. 3 is a cross-sectional view of an orbital welder 300 capable of forming a flat "T" weld. Orbital welder 300 includes an insulating housing 302, a tube clamp 304, a "T" fitting clamp 306, a rotor 308, a weld tip 310, and a rotation and voltage controller 312.
Orbital welder 300 functions similarly to orbital welder 100. Clamps 304 and 306 hold a tube 314 and a T-fitting 316 in position and at a common voltage. Rotation and voltage controller 312 causes rotor 312 to rotate about an axis 318, and applies a high voltage, via rotor 308, to weld tip 310. As rotor 308 rotates about axis 318, a weld 320 is formed between the open ends of tube 314 and T-fitting 316.
FIG. 4 is a perspective view of T-fitting 316. In order to make T-fitting 316 from a standard piece of tube stock 402, an opening 404 is first cut or ground into the tube stock 402. Next, an extrusion process is required to draw the tube material surrounding opening 404 into an extended portion 406 defining a flat circular opening 408. Because the extrusion process is relatively complex, workers cannot weld T-joints quickly and easily on job sites, from standard tube stock. Additionally, for commonly used 0.25 in. O.D. tubing, the extrusion process is generally limited to tubes with a wall thickness of 0.028 in. or less, and is therefore unavailable for the preferred 0.035 in. walled tubing.
What is need is an orbital welder capable of welding T-joints and cross-joints from standard tube stock. What is also needed is an orbital welder which facilitates easy alignment of the tube pieces which are to be welded. What is also needed is an orbital welder with that facilitates visual confirmation of proper alignment.